This invention relates generally to processor-based systems and, more particularly, to storage interfaces or links utilized to connect mass storage devices with a processor-based device.
Many competing storage interface standards have been defined, playing a critical role in creating more affordable systems with performance, reliability, scalability, and interoperability generally needed for a host of storage applications. For example, a storage interface standard involving point-to-point connectivity may provide significant performance and reliability advantage over a shared connectivity approach. Other examples of serial storage interfaces may have different topology. For instance, Fibrechannel generally is connected in a loop with devices daisy-chained together, while another serial storage interface is connected in a hub and star hierarchy. Another storage interface standard uses a parallel protocol for connecting master and slave devices on a single, parallel cable in one specific example of legacy parallel AT attachment (ATA). Nonetheless, a storage interface may enable a controller to communicate with a given storage drive or device through a port to which it is connected. Because only one storage drive or device may be directly connected to a host via a dedicated link on a port, the entire port may have to be dedicated to that storage device itself. For example, a master storage device connected to a port cannot share the same port with another device in a slave mode. As a result, loss of the port alone causes fewer storage interface-compliant devices to be plugged into a system.
While a parallel storage interface may form a cable nest of multiple conductor ribbon cables affecting system's airflow and cooling, a serial storage interface may not allow communication to a slave device on a serialized link or a cable. When using a standard set of protocols, a single, fully-equipped storage interface-compliant device that is capable of interpreting all commands relating to the protocols may only be deployed. Additionally, in some parallel storage interfaces, the drives or devices on a shared common cable may need to be jointly qualified, resulting in unnecessary overhead in order to qualify all possible combinations of drives or devices sharing the same cable. In view of the problems set forth above and without incurring the loss of a port, an additional drive or device may not be desirably added on the same port.
Thus, there is a continuing need for better ways to connect mass storage devices to a processor-based device, especially in processor-based systems.